Rotor repair method and rotor repair apparatus

ABSTRACT

A to-be-repaired damaged part, which occurs in a rotor, is removed and shaped by machining or grinding. The shaped surface, from which the to-be-repaired damaged part is removed in the step, is roughened by a blasting process. A coating is formed on the surface, which is roughened in the step, by a high-velocity flame spray apparatus. The coating, which is formed in the step, is finished by machining or polishing. A defect inspection is performed to check presence/absence of a defect. A dimensional/quality inspection is performed for the part repaired in the step.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation Application of PCT Application No.PCT/JP2004/012061, filed Aug. 23, 2004, which was published under PCTArticle 21(2) in Japanese.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotor repair method and a rotorrepair apparatus for repairing a rotor, which is used, for example, in aturbine generator, and a damaged part of which is repaired by forming athermal spray coating.

2. Description of the Related Art

FIG. 7 is a schematic view showing the structure of a conventionalturbine generator. The turbine generator generally comprises a stator 2,a rotor 1, and a journal bearing 3 that rotatably supports the rotor 1.

The stator 2 comprises a stator core 2 a and a stator coil 2 b that isinserted in slots formed in the stator core 2 a.

The rotor 1 comprises a rotor coil 1 a that is inserted in slots (notshown) formed in a rotor main body; an end ring 1 b for fixing the rotorcoil 1 a; a fan 1 c for cooling the rotor 1 and stator 2; a rotorcoupling id that is provided at an end portion of the rotor 1 forcoupling to a gas turbine or a steam turbine; and a journal 1 e that isrotatably supported by the journal bearing 3.

The large-sized rotor 1 of a hydraulic turbine, a gas turbine, a steamturbine or the like, or the rotor 1 of a generator or the like, may bedamaged during transportation or due to driving. Serious considerationhas been given to measures for repair of the damage part, such ascutting of the damaged part of the rotor 1 by machining, andimprovements of peripheral devices necessary for the repair.

For example, as shown in FIG. 8A, a damaged part 4 may occur in thejournal 1 e of rotor 1, which is rotatably supported by the journalbearing 3 (not shown), due to foreign matter, abnormality in driving andthe life of parts.

In this case, in order to remove the damaged part 4 in the journal 1 e,the diameter if of the rotor (rotor diameter) is reduced by a dimension1 g by machining, etc., as shown in FIG. 8B.

The journal bearing 3 needs to be re-manufactured so as to conform tothe rotor diameter if that is reduced by 1 g. This leads to a decreasein operation rate due to long-time halt of driving, and to an increasein manufacturing cost.

In addition, as shown in FIG. 9A, when an erroneously machined part 5occurs in a machining process step in the manufacture of the rotor 1,design alteration or the like is performed each time such part 5 occurs,and the abnormality of the erroneously machined part 5 is eliminated bymachining, etc., as shown in FIG. 9B. This may cause a decrease inperformance or reliability of an apparatus using the rotor.

Repair by a high-heat-input process, such as overlaying, is a possiblechoice as the repair work for the damaged part 4 or erroneously machinedpart 5. However, since the rotor 1 rotates at high speed, it is notpossible to use a repair process which may cause damage to the rotorbase material. In addition, deformation may occur due to high heatinput, and heat treatment, such as thermal refining, may becomenecessary. The heat treatment poses a serious problem from thestandpoint of a decrease in repair time and repair cost.

Patent document 1 and patent document 2 (mentioned below) discloseconventional methods of manufacturing rotary bodies. The manufacturingmethod of patent document 1 aims at enhancing wear resistance of an oilpump or other rotary machines, without causing a gap due to a differencein thermal expansion or causing seizure at a sliding part where a casingand a rotary member are put in contact. To achieve this object, inpatent document 1, a wear-resistant material, such as steel, is sprayedby a thermal spray apparatus to a contact part between a light-alloycasing and a light-alloy rotary body which is accommodated within thelight-alloy casing. Thereafter, a pressing process, such as shotpeening, is applied to at least an edge part of the rotary body.

The object of patent document 2 is to provide a thermal-sprayed roll onwhich an excellent functional thermal spray coating is formed, and whichis usable as an iron-making process without the possibility of peelingof the coating. To achieve this object, a thermal spray coating with acomposition of tungsten carbide (WC) and cobalt (C), which has athickness of 20 μm to 200 μm, is formed on the surface of a roll basemember. The thermal spray coating is further coated with a functionalcoating formed of a metal, a metal compound, a ceramic or a cermet,which mainly comprises any one or two of Mo, Ni, Cr, Co, Al, Y, Al₂O₃,Cr₃C₂ and TiO₂.

However, even if the rotor is manufactured, as disclosed in patentdocuments 1 and 2, the function of the thermal-spray-coated part willdeteriorate and may be damaged. In these techniques, at the time ofmanufacture, the surface function is provided by the thermal spraycoating. These techniques are not intended to repair or reproduce adamaged part by means of thermal spray coating. There is the problemthat when the thermal-sprayed part or the rotary body, such as the rotoror roll, is damaged, the damaged part cannot be repaired.

Patent document 1 is Jpn. Pat. Appln. KOKAI Publication No. 4-232244.Patent document 2 is Jpn. Pat. Appln. KOKAI Publication No. 9-20975.

The present invention has been made to solve the above problem, and theinvention provides a rotor repair method and a rotor repair apparatusfor repairing a damaged part of a rotor, with little thermal damage to arotor base material, while achieving a decrease in time for periodicalmaintenance and repair cost and enhancing the reliability of apparatus.

BRIEF SUMMARY OF THE INVENTION

According to the present invention corresponding to claim 1, there isprovided a rotor repair method wherein a thermal spray coating is formedon a to-be-repaired damaged part of a rotor, which is rotatablysupported by a bearing, by a high-velocity flame spray apparatus with aflame velocity of 600 m/sec to 3000 m/sec and with a particle velocityof 500 m/sec to 2000 m/sec, whereby the damaged part is repaired.

According to the present invention corresponding to claim 12, there isfurther provided a rotor repair apparatus comprising: a thermal sprayunit including a thermal spray gun for forming a thermal spray coatingon a to-be-repaired part of a rotor which is to be repaired, whilerotating the rotor; and a driving unit which moves the thermal spray gunin a horizontal direction or in a vertical direction to a rotationalaxis of the rotor at a movement speed with a pitch of 0.1 mm/sec.

The present invention can provide a rotor repair method and a rotorrepair apparatus for repairing a damaged part of a rotor, with littlethermal damage to a rotor base material, while achieving a decrease intime for periodical maintenance and repair cost and enhancing thereliability of apparatus.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a flow chart illustrating a rotor repair method byhigh-velocity flame spray according to the present invention;

FIG. 2 is a structural view showing a state in which a damaged part of arotor is repaired by a high-velocity flame spray step illustrated inFIG. 1;

FIG. 3A shows an experimental result which indicates a defect occurrenceratio at a boundary plane at a time when a coating is formed by thehigh-velocity flame spray step for repairing the damaged part, asillustrated in FIG. 1;

FIG. 3B is a cross-sectional view of a boundary plane in a case wherethe finishing angle of a corner portion at the boundary plane between ato-be-removed damaged portion and a non-damaged portion of the rotor isset to be greater than 45° in the method illustrated in FIG. 1;

FIG. 3C is a cross-sectional view of a boundary plane in a case wherethe angle (i.e. the finishing angle of a corner portion) of an inclinedsurface of a grooved part at both ends of the boundary plane between ato-be-removed damaged portion and a non-damaged portion of the rotor isset to be 45° or less (excluding 0°) in the method illustrated in FIG.1;

FIG. 4 shows an X-ray residual stress measurement result, whichindicates a residual stress in the coating in the present invention;

FIG. 5A is a front view showing the state in which the rotor is repairedby the high-velocity flame spray coating according to the invention atan on-site generation plant;

FIG. 5B is a left side view of FIG. 5A;

FIG. 5C is a right side view of FIG. 5A;

FIG. 6 is a schematic view showing the state in which a thermal sprayrepair system according to another embodiment of the invention, which isconfigured for repair of an on-site generation plant, is mounted on amovable vehicle;

FIG. 7 is a schematic view showing the structure of a conventionalturbine generator;

FIG. 8A is a schematic view showing a damaged part occurring in a rotorjournal which is supported by a conventional journal bearing;

FIG. 8B is a schematic view showing the state in which the damaged partoccurring in the rotor journal, which is supported by the conventionaljournal bearing, is removed;

FIG. 9A is a schematic view showing the state in which an erroneouslymachined part has occurred in a machining process step at the time ofmanufacturing a conventional rotor; and

FIG. 9B is a schematic view showing the state in which an erroneouslymachined part has occurred in a machining process step at the time ofmanufacturing a conventional rotor.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying drawings. FIG. 1 is a flow chartillustrating a rotor repair method 10 according to a first embodiment ofthe present invention. This method will be described below in detail.

In a first step S1, for example, a repair worker finds, by visualobservation, a damaged part, which is to be repaired, in the journal 1 eof the rotor 1. The damaged part is completely removed and shaped bymachining or grinding, as will be described later.

Subsequently, in a second step S2, the shaped surface, from which theto-be-repaired damaged part is removed in the first step S1, isroughened by a blasting process using a blasting material and processconditions (to be described later).

In a third step S3, a coating is formed on the surface, which isroughened in the second step S2, by a high-velocity flame spray(HP/HVOF: High Pressure/High Velocity Oxygen Fuel) apparatus (to bedescribed later).

In a fourth step S4, the coating, which is formed in the third step S3,is finished by machining or polishing.

In a fifth step S5, a defect inspection is performed to checkpresence/absence of a defect.

In a sixth step S6, a dimensional/quality inspection is performed forthe part repaired in the fifth step S5.

In the first step S1, the damaged part of the rotor 1 is completelyremoved and shaped, in order to prevent development or enlargement ofthe defect due to damage in a subsequent repair step, thereby enhancingthe reliability of the apparatus.

The amount of removal and the range of removal of the damaged part needto be judged on the basis of the depth of the damage occurring in thedamaged part and the area of the damaged part. From the standpoint ofpreventing a decrease in strength and degradation in reliability, it isdesirable to reduce the to-be-removed part to a minimum necessary range.

In the first step S1, when the to-be-repaired damaged part of thejournal le is removed and shaped, the damaged part is removed, forexample, in an isosceles-trapezoidal shape, as shown in across-sectional view of FIG. 2. Specifically, each of both axial endportions, that is, a boundary plane 4 c between a to-be-removed damagedportion 4 a and a non-damaged portion 4 b, is shaped so as to have abottom surface portion and an inclined surface portion. The bottomsurface portion is formed parallel to the rotational axis. The inclinedsurface portion (sloping portion) 4 d is formed at each of both endportions of the bottom surface portion, at an angle of 45° or less(excluding 0°) to an extension line including the bottom surfaceportion.

In the second step S2, the blasting process is performed. Thereby, thesurface of the base material of the rotor 1 can uniformly be roughened,and a defect, which occurs at the boundary plane 4 c when the coating isformed by the high-velocity flame spray in the third step S3, can bereduced. Further, the contact of the coating is improved, and thereliability of the spray coating repair can be enhanced.

A more advantageous effect is obtained if the boundary plane 4 c betweenthe to-be-removed damaged portion 4 a and the non-damaged portion 4 b isshaped so as to have inclined surface portions 4 d at a low angle of 30°or 15°.

The inclined surface 4 d may be replaced with an arcuate surface.

In the second step S2, the shaped surface, from which the to-be-repaireddamaged part is removed in the first step S1, is roughened by theblasting process. Thereby, the spray material, which is sprayed by thehigh-velocity flame spray in the third step S3, firmly adheres to thesurface of the rotor 1, and the close contact of the formed coating isimproved.

The blasting material in the blasting process of the second step S2 isparticles of alumina, silica, glass beads, light-alloy material, cork,rubber, etc. In the blasting process, an air pressure or gas pressure isset at 2 kg/cm² to 6 kg/cm² (0.2 to 0.6 MPa). This makes it possible toroughen the surface of the rotor 1 without deformation. When the surfaceis roughened, blasting is performed at an angle of 45° to 90° to thesurface of the base material of the rotor 1. Thereby, the surface of thebase material of the rotor 1 can be roughened three-dimensionally, andthe close contact of the coating can be improved.

In the third step S3, the coating is formed using the high-velocityflame spray apparatus. Thereby, the spray material is sprayed at avelocity which is two times or three times higher than the acousticvelocity, the spray material is caused to impinge upon the surface ofthe base material of the rotor 1 at high velocity, and the coating isformed. With use of the high-velocity flame spray apparatus, it becomespossible to obtain a coating with less pores, high density, highadhesion and high interparticle coupling force, and to enhance thereliability of the apparatus by repair. In addition, if the spraymaterial is sprayed at a velocity which is two times or three timeshigher than the acoustic velocity, the spray material is caused toimpinge upon the surface of the base material of the rotor 1 at highvelocity and the coating is formed, a compressive residual stress occursin the coating due to a peening effect and a crack or peeling of thecoating can be reduced. Furthermore, the coating with a thickness of 8.0mm or more at maximum can be formed.

When the third step S3 is performed, the high-velocity flame stray isperformed at an angle of 45° to 90° to the surface of the base materialof the rotor 1. Thereby, the close contact of the coating on the basematerial of the rotor 1 can be improved, and it is possible to obtainthe coating with less pores, high density and high interparticlecoupling force.

In the fourth step S4, the spray coating, which is formed in the thirdstep S3, is finished by machining or polishing. Thereby, the diameter ofthe rotor at the repaired part, which is provided with the coating bythe high-velocity flame spray in the third step S3 so that the rotor mayhave a greater diameter than the initial diameter (e.g. 1 f in FIG. 8 or9), is restored to the initial rotor diameter 1 f. In addition, thesurface roughness of the rotor 1 is restored to the design value. Atthis time, the reliability is remarkably enhanced by performingfinishing so that no stepped part is formed at the boundary planebetween the repaired part and the surface of the base material of therotor 1.

The defect inspection in the fifth step S5 for checking thepresence/absence of a defect and the dimensional/quality inspection inthe sixth step S6 for the repaired part are necessary steps forproviding a non-defective product. A defect facilitates peeling of thecoating or running of a crack, and is a factor that degrades theperformance of the repaired part. By eliminating a defect at therepaired part, the reliability of the repaired product can be improved.

FIG. 2 illustrates the high-velocity flame spray in the third step S3 inFIG. 1. FIG. 2 shows the state in which the damaged part 4 of the rotor1, which is rotatably supported by the journal bearing 3 shown in FIG. 7or a thrust bearing (not shown), is repaired by using a high-velocityflame spray apparatus 6, which is described below. The high-velocityflame spray apparatus 6 includes a spray gun 6 b which is capable ofadjusting the velocity of a flame 6 a at 600 m/sec to 3000 m/sec, andthe velocity of particles at 500 m/sec to 2000 m/sec.

The conditions for the high-velocity flame spray in the third step S3are as follows. For instance, a spray apparatus 6 which is manufacturedby TAFA (model No. JP5000) is used. The base material of the rotor isNiCrMoV steel. The coating, that is, spray powder, is NiCrMoV steel.Fuel is kerosene and oxygen. A 4-inch gun barrel is provided. The flowrate of oxygen is 1850 scfh (870 l/min). The supply amount of kerosenefuel is 5.7 gph (22 l/hr). The combustion pressure is 97 psi (0.7 MPa).The velocity of movement of the gun is 350 mm/sec. The powder supplyamount is 40 g/min, and the distance for spraying is 380 mm.

In the case where the rotor is repaired under the above-describedconditions, when the damaged part is removed and shaped by machining orgrinding in the first step, the boundary plane 4 c between theto-be-removed damaged portion 4 a and the non-damaged portion 4 b isshaped so as to have the inclined surface 4 d, or an arcuate surface, atan angle of 45° or less (excluding 0°). Thereby, as shown in FIG. 3, thedefect occurrence ratio of the boundary plane 4 c can be reduced whenthe coating is formed by the high-velocity flame spray.

Specifically, FIG. 3A shows the defect occurrence ratio of the boundaryplane 4 c at the time when the coating is formed by the high-velocityflame spray apparatus 6 (i.e. the defect occurrence ratio at 5measurement points on the corner portion of repaired part 9). On theother hand, FIG. 3B is a cross-sectional view of the boundary plane 4 cin the case where the finishing angle of the corner portion at theboundary plane between the to-be-removed damaged portion 4 a of thedamaged part 4 and the non-damaged portion 4 b is set to be greater than45°. In this case, a defect occurs at the corner portion (indicated byarrows).

FIG. 3C is a cross-sectional view of the boundary plane 4 c in the casewhere the angle (i.e. the finishing angle of the corner portion) of theinclined surface 4 d of the grooved part at both ends of the boundaryplane 4 c between the to-be-removed damaged portion 4 a of the damagedpart and the non-damaged portion 4 b is set to be 45° or less (excluding0°). In this case, no defect occurs at the corner portion. In FIG. 3Band FIG. 3C, numeral 7 denotes a spray material that is sprayed at theto-be-removed portion 4 a, numeral 8 denotes the sprayed coating, andnumeral 9 denotes the repaired part.

As is clearly understood from FIG. 3, if the corner portion of therepaired part 9 is formed to have the inclined surface with the angle of45° or less (excluding 0°) or the arcuate surface, the defect occurrenceratio is decreased to 10% or less, and a defect will hardly occur. Thus,the defect occurrence ratio can be reduced, the close contact of thespray coating can be improved, and the reliability of repair by thermalspray can be enhanced.

By contrast, if the angle of the inclined surface of the corner portionis set to be greater than 45°, the defect occurrence ratio increases to80% or more, and a considerable number of defects will occur at thecorner portion.

The spray material 7 that is used is a coating material having a similarchemical composition and material characteristic to the rotor 1 to berepaired. In the repair 10 of the rotor 1, the spray coating 8 is formedin a range of 0.020 mm to 8.0 mm. The surface of the coating is machinedor polished to have a surface roughness of 6.5 S or less (excluding 0 S;S represents finishing roughness) and to have a predetermined thickness.

The reason why the coating material having the similar chemicalcomposition and material characteristic to the to-be-repaired rotor 1 isused is that deformation due to stress or heat occurring in the repairedpart 9 of the rotor 1 has to be prevented during the halt of driving,during driving and during abnormal driving. As regards the slidingcharacteristics, a performance similar to the material of the rotor 1can be obtained. Specifically, if a material different from the basematerial of the rotor 1 is used for the repaired part 9, deformation orthermal stress occurs due to a difference in thermal expansioncoefficient or thermal conductivity. This leads to occurrence ofvibration at the time of rotation of the rotor 1, and considerablydegrades the reliability of the apparatus. If a thick film can be formedby high-velocity flame spray, the same shaping function as withoverlaying can be attained, and the damaged part 4 or the erroneouslymachined part 5 can easily be repaired without causing damage to thebase material of the rotor 1.

In the fourth step S4, the spray coating 8, which is formed in the thirdstep S3, is finished by machining or polishing. Thereby, the diameter ofthe rotor at the repaired part 9, which is provided with the spraycoating 8 by the high-velocity flame spray so that the rotor may have agreater diameter than the initial rotor diameter 1 f in consideration ofmechanical finishing, is restored to the initial rotor diameter if, asshown in FIG. 7 and FIG. 8. In addition, the surface roughness of therotor 1 is restored to a design value of 6 S or less. At this time, thefinishing needs to be performed so that no stepped part is formed at theboundary plane 4 c between the repaired part 9 and the surface of thebase material of the rotor 1.

As regards the thickness of the coating at the time of repair, as shownin the X-ray residual stress measurement result in FIG. 4, the coatinghas a compressive residual stress lib up to 8.0 mm. At 8.0 mm or more,the residual stress 11 of the coating changes to a tensile residualstress 11 a. It is understood that on the tensile stress side, peelingor cracking of the coating occurs, and the thick film cannot be formed.In the current situation, the maximum thickness is 8.0 mm, and the thickfilm can be formed in this range.

FIG. 5 is a view for describing a second embodiment of the presentinvention. The repair method 10 for the rotor 1 by the high-velocityspray apparatus 6 in the third step S3 is implemented at one of thelocation of a generation plant on the site (a turbine generatorincluding a rotor to be repaired) and the location of a repair factory,or at the location where these are disposed together. FIG. 5A is a frontview, FIG. 5B is a left side view of FIG. 5A, and FIG. 5C is a rightside view of FIG. 5A. The structure shown comprises a rotor 1 to berepaired at the site; a rotor driving unit 14; a high-velocity flamespray apparatus 6 including a spray gun 6 b for forming a spray coating8; a horizontal spray gun driving unit 15 for moving the spray gun 6 bin a direction horizontal to the rotational axis of the rotor 1; and avertical spray gun driving unit 16 for moving the spray gun 6 b in adirection perpendicular to the rotational axis of the rotor 1. Dependingon uses, the high-velocity flame spray apparatus 6 may not be providedwith the vertical spray gun driving unit 16 of the horizontal spray gundriving unit 15 and vertical spray gun driving unit 16.

The repair method 10 for the rotor 1 is normally implemented at anassembly factory. However, if repair is performed at the on-sitegeneration plant where the to-be-repaired apparatus is installed, thetime period for repair and the cost for repair can be reduced.

In usual cases, when repair is performed at the assembly factory, theto-be-repaired object is packaged and transported from the generationplant. A serious problem arises when the to-be-repaired object istransported, in particular, from a foreign country, although a similarproblem arises with domestic transportation. When the to-be-repairedobject is transported from a foreign country to the assembly factory, atime period of, e.g. more than two months at maximum is required fromthe packing, transportation and customs clearance to the beginning ofrepair. The operation rate decreases due to the halt of the operation ofthe plant. As regards the repair that can be performed at the on-siteplant, it is effective to perform the repair at the on-site generationplant. Only the indispensable, necessary repair items are conducted inthe repair factory or assembly factory. Thereby, in the case of theon-site repair, the repair can be completed within two weeks at most.

In the case where the rotor 1 is repaired at the assembly factory, thethermal spray equipment, which is installed as factory equipment, can beused. The thermal spray equipment installed at the factor includes asound-proof chamber, a spraying robot, a control unit, a dust collectingunit, a cooling water chiller, a crane, and a rotor driving unit.

However, at the on-site generation plant, spraying equipment for repairis rarely installed. Thus, when the rotor 1 is to be repaired at theon-site generation plant, it is necessary to transport to the on-sitegeneration plant such components as a sound-proof chamber, a sprayrobot, a control unit, a dust collecting unit, a cooling water chiller,a crane and a rotor driving unit, and to assemble them at the site.

However, the sizes of the sound-proof chamber, spray robot, controlunit, dust collecting unit and rotor driving unit are large and are ofthe factory-installation type. There are restrictions to thetransportation of them to the on-site generation plant, and suchtransportation is difficult in many cases.

Under the circumstances, it is necessary to provide devices which can besubstituted for the spraying equipment capable of repairing the rotor 1at the on-site generation plant, in particular, for the spraying robot.

FIG. 5 shows repair equipment which is substituted for thefactory-installed spraying robot when the spray coating 8 is formed forrepair. When repair is conducted, the spray gun 6 b is fixed to thespray gun driving units 15 and 16 which can arbitrarily move the spraygun 6 b in the horizontal direction 15 a and vertical direction 16 arelative to the rotational axis of the rotor 1.

The robot is used if it can be transported to the on-site generationplant as the equipment capable of arbitrarily moving the spray gun inthe horizontal direction 15 a and vertical direction 16 a. If the robotcannot be transported, the spray gun driving units 15 and 16, which usethe driving mechanisms including ball screws and stepping motors, areemployed.

In this case, the equipment used is configured to include a spray gunmovement table 17 which moves the spray gun 6 b in the horizontaldirection 15 a and vertical direction 16 a relative to the rotationalaxis of the rotor 1, and configured to be able to control the spray gunmovement speed with a pitch of 0.1 mm/sec. Moreover, while the rotor 1is being rotated in a direction of arrow 14 a shown in FIG. 5A, thespray gun 6 b is moved in the horizontal direction 15 a to performrepair by thermal spray.

When the rotor 1 is to be repaired at the on-site generation plant, therepair is performed by fixing the spray gun 6 b to the spray gun drivingunits 15 and 16 which can arbitrarily move the spray gun 6 b in thehorizontal direction 15 a and vertical direction 16 a relative to therotational axis. Thereby, even in the case where the to-be-repaired part9 of the rotor 1 is not specified, the spray gun 6 a can be moved to anarbitrary position, and an optimal range for repair can arbitrarily beset. In particular, in the case of moving the spray gun in the verticaldirection 16 a, it is necessary to set the spray gun 6 b at the centerof the rotor diameter if. The adjustment can be performed in units ofmm, and thermal spray repair with high precision can advantageously beperformed.

At the time of thermal spray repair, the spray gun 6 b is moved in thehorizontal direction 15 a while the rotor 1 is being rotated (arrow 14a). This aims at uniformly forming the spray coating 8 on the outerperipheral surface of the rotor 1.

In general, in the case of planar thermal spray, the spray gun 6 b isfixed to the robot arm, and the arm of the robot is moved to performspraying. However, in the case of performing spray on a cylindricalsurface, it is difficult to perform spray while rotating the arm of therobot in the direction of arrow 14 a. It is thus necessary to performspray by rotating the cylindrical to-be-sprayed object itself in thedirection of arrow 14 a. Consequently, in the case of repair at theon-site generation plant, the rotor 1 is rotated in the direction ofarrow 14 a by the device capable of rotating the rotor 1 in thedirection of arrow 14 a, for example, a rotating device having arotating mechanism such as a lathe. Thus, the surface of theto-be-repaired part 9 of the rotor 1 is repaired. Thereby, the spraycoating to be formed can uniformly formed on the outer periphery of therotor 1, and the reliability of repair can be enhanced.

The spray gun driving units 15 and 16 using the driving mechanismsincluding the ball screws and stepping motors are used. Thereby, thespray gun movement speed can be controlled with a pitch of 0.1 mm/sec,and the spray gun 6 b can continuously and stably be moved whilewobbling or vibration of the spray gun 6 b during movement can beprevented.

In order to set the spray gun movement speed within the normal range of250 to 400 mm/sec., it is necessary to alter the rotational speed of theto-be-repaired rotor 1 and the spray gun movement speed each time thediameter if of the to-be-repaired rotor is varied. At this time, bycontrolling the spray gun movement speed with a pitch of 1 mm/sec, noproblem arises with almost all values of the rotor diameter 1 f.

FIG. 6 shows a third embodiment of the invention which relates to repairat the one-site generation plant. A thermal spray repair system 24,which comprises a spray gun 6 b, spray gun driving units 15 and 16, asimplified sound-proof chamber 19, a cooling water chamber 20, a dustcollecting unit 21, a generator 22 and a blasting unit 23, is mounted ona movable vehicle 25, so that repair 10 may be performed on the sitewith ease.

By simply transporting the thermal spray repair system 24 mounted on thevehicle 10, it becomes unnecessary to consume a great deal of labor inarranging for traffic means or transporting means both at domestic areaswith inconvenient transportation means and at foreign countries. Repairwork for the on-site generation plant can be conducted within a shorttime period.

The present invention is usable in repairing a rotor of a hydraulicturbine, a gas turbine, a steam turbine, etc., or a rotor of agenerator, etc.

1. A rotor repair method wherein a thermal spray coating is formed on ato-be-repaired damaged part of a rotor, which is rotatably supported bya bearing, by a high-velocity flame spray apparatus with a flamevelocity of 600 m/sec to 3000 m/sec and with a particle velocity of 500m/sec to 2000 m/sec, whereby the damaged part is repaired.
 2. The rotorrepair method according to claim 1, wherein when the thermal spraycoating is formed on the damaged part of the rotor and the damaged partis repaired, a thermal spray repair material, which has a chemicalcomposition and material characteristics similar to the damaged part ofthe rotor, is used.
 3. The rotor repair method according to claim 1,wherein when the thermal spray coating is formed on the damaged part ofthe rotor and the damaged part is repaired, the thermal spray coating ina range of 0.05 mm to 8.0 mm is formed on the to-be-repaired part of therotor.
 4. The rotor repair method according to claim 1, wherein when thethermal spray coating is formed on the damaged part of the rotor and thedamaged part is repaired, the to-be-repaired part is subjected inadvance to a surface formation process by machining or grinding, and theto-be-repaired part is roughened by a blasting process.
 5. The rotorrepair method according to claim 4, wherein when the to-be-repaired partis subjected to the surface formation process by machining or grinding,a shape of a groove at both ends of the repaired part is formed to havean inclined surface at 45° or less (excluding 0°) or an arcuate surface.6. The rotor repair method according to claim 1, wherein when thethermal spray coating is formed on the damaged part of the rotor and thedamaged part is repaired, a surface of the formed coating is finished inadvance to have a surface roughness of 6.5 S or less (excluding 0 S) bymachining or polishing.
 7. The rotor repair method according to claim 1,wherein when the thermal spray coating is formed on the damaged part ofthe rotor and the damaged part is repaired, repair is performed at oneof a location of a generation plant, in which the rotor is disposed, anda location of a repair factory, or at a location where the generationplant and the repair factory are disposed together.
 8. The rotor repairmethod according to claim 1, wherein when the thermal spray coating isformed on the damaged part of the rotor and the damaged part isrepaired, thermal spray is performed by horizontally moving a thermalspray gun of the high-velocity flame spray apparatus while the rotor isbeing rotated.
 9. The rotor repair method according to claim 1, whereinwhen the thermal spray coating is formed on the damaged part of therotor and the damaged part is repaired, repair is performed by fixing athermal spray gun of the high-velocity flame spray apparatus toequipment capable of arbitrarily moving the thermal spray gun of thehigh-velocity flame spray apparatus in a horizontal direction and aperpendicular direction to a rotational axis of the rotor.
 10. The rotorrepair method according to claim 9, wherein a robot or a drivingmechanism including a ball screw and a stepping motor is used as theequipment capable of arbitrarily moving the thermal spray gun of thehigh-velocity flame spray apparatus in the horizontal direction andperpendicular direction.
 11. The rotor repair method according to claim10, wherein when the thermal spray gun is moved in the horizontaldirection and vertical direction to the rotational axis of the rotor,the movement is controlled with a movement speed of a pitch of 0.1mm/sec.
 12. A rotor repair apparatus comprising: a thermal spray unitincluding a thermal spray gun for forming a thermal spray coating on ato-be-repaired part of a rotor which is to be repaired, while rotatingthe rotor; and a driving unit which moves the thermal spray gun in ahorizontal direction or in a vertical direction to a rotational axis ofthe rotor at a movement speed with a pitch of 0.1 mm/sec.